PLATE CLXXI. 



Gmelin, in his edition of the Sy sterna Nature, neglects to insert 

 this species, for what reason we are at a loss to conceive. The 

 specimens we possess of this rare shell, from the warmer parts of 

 Europe, are larger than those found on our* coast. In different 

 specimens we observe that the striae are liable to vary both in form 

 and number, some shells appearing much more strongly reticulated 

 than others. 



